# \#point-source **URL:** https://fenicsproject.discourse.group/tag/point-source/19.md [Latest](https://fenicsproject.discourse.group/latest.md) · [Categories](https://fenicsproject.discourse.group/categories.md) · [Tags](https://fenicsproject.discourse.group/tags.md) --- ## [How to correctly apply a point source in nonlinear problem in fenicsx](https://fenicsproject.discourse.group/t/how-to-correctly-apply-a-point-source-in-nonlinear-problem-in-fenicsx/16314)
**Author:** [@noir](https://fenicsproject.discourse.group/u/noir)\ **Replies:** 1\ **Last updated:** [March 31, 2026, 12:19pm UTC](https://fenicsproject.discourse.group/t/how-to-correctly-apply-a-point-source-in-nonlinear-problem-in-fenicsx/16314 "2026-03-31T12:19:13Z")
I am simulating a problem where flow injected through a point source on a horizontal plane. The axisymmetric dimensionless equation is \\begin{aligned} xu\_t+\\left(x\\partial\_x+1\\right)\\Gamma&=\\frac{\\delta(x)}{2\\pi } \\qua… --- ## [Vectorial Point Source Term (Stokes equations)](https://fenicsproject.discourse.group/t/vectorial-point-source-term-stokes-equations/15082)
**Author:** [@andyscott93](https://fenicsproject.discourse.group/u/andyscott93)\ **Replies:** 9\ **Last updated:** [January 15, 2025, 5:10am UTC](https://fenicsproject.discourse.group/t/vectorial-point-source-term-stokes-equations/15082 "2025-01-15T05:10:55Z")
Hi. I want to solve the Stokes equations in a unit cube with no slip boundary conditions in all faces of the cube and one point force in the center of the cube (pointing, for example, along the z axis). This is to solve … --- ## [Solving dynamic linear system without integrating the linear form](https://fenicsproject.discourse.group/t/solving-dynamic-linear-system-without-integrating-the-linear-form/15330)
**Author:** [@Eduardo\_Firvida](https://fenicsproject.discourse.group/u/Eduardo_Firvida)\ **Replies:** 2\ **Last updated:** [October 26, 2024, 2:32am UTC](https://fenicsproject.discourse.group/t/solving-dynamic-linear-system-without-integrating-the-linear-form/15330 "2024-10-26T02:32:09Z")
This question is strongly related to this other thread. So the main idea is: I’m triying to couple DOLFINx via preCICE by myself, because the current adapter can solve 3D linear elastic problems at the moment. In t… --- ## [Use Previous Solution as Initial Guess](https://fenicsproject.discourse.group/t/use-previous-solution-as-initial-guess/15316)
**Author:** [@andyscott93](https://fenicsproject.discourse.group/u/andyscott93)\ **Replies:** 1\ **Last updated:** [July 22, 2024, 5:33pm UTC](https://fenicsproject.discourse.group/t/use-previous-solution-as-initial-guess/15316 "2024-07-22T17:33:01Z")
Hi. I have a code written using Legacy Dolfin to solve the Green’s function of the Stokes flow. Actually I solve for a force dipole, defining two point forces instead of one, as you see in the code. What I want to do is … --- ## [How to construct a sparse matrix used for calculating function values at multiple points](https://fenicsproject.discourse.group/t/how-to-construct-a-sparse-matrix-used-for-calculating-function-values-at-multiple-points/13081)
**Author:** [@Junxiong\_Jia](https://fenicsproject.discourse.group/u/Junxiong_Jia)\ **Replies:** 9\ **Last updated:** [February 5, 2024, 2:13pm UTC](https://fenicsproject.discourse.group/t/how-to-construct-a-sparse-matrix-used-for-calculating-function-values-at-multiple-points/13081 "2024-02-05T14:13:37Z")
Hi everyone. Recently, I try to convert my program based on FEniCS 2019 to the new version FEniCSx. I meet a problem for transforming the following code to the current version due to lack of some functions, e.g., dolfin\_… --- ## [How to define my Dirac Delta only on the boundary](https://fenicsproject.discourse.group/t/how-to-define-my-dirac-delta-only-on-the-boundary/12739)
**Author:** [@gperezb1](https://fenicsproject.discourse.group/u/gperezb1)\ **Replies:** 1\ **Last updated:** [January 21, 2024, 3:15pm UTC](https://fenicsproject.discourse.group/t/how-to-define-my-dirac-delta-only-on-the-boundary/12739 "2024-01-21T15:15:45Z")
Hello everybody, I have implemented a Dirac Delta UserExpression on dolfin legacy, however, it proves to be quite a slow implementation. I know that the points that I’ll be applying my Dirac Delta to are located over th… --- ## [PointSource in dolfinx](https://fenicsproject.discourse.group/t/pointsource-in-dolfinx/8337)
**Author:** [@bay\_swiss](https://fenicsproject.discourse.group/u/bay_swiss)\ **Replies:** 21\ **Last updated:** [December 18, 2023, 8:15am UTC](https://fenicsproject.discourse.group/t/pointsource-in-dolfinx/8337 "2023-12-18T08:15:04Z")
Hello everyone, I work with inhomogeneous Helmholtz equation and i wonder if the PointSource that was available in dolfin will be implemented in dolfinx. Right now i am approximating it with the following steps: delt…